Kilometre zero (or km 0), also known as zero mile marker or zero milepost, is a particular location (usually in the nation's capital city) from which traveled distances are traditionally measured, as in distance markers. Historically, they were markers where drivers could set their odometers to follow the directions in early roaming guidebooks.
One such marker is the Milliarium Aureum ("Golden Milestone") of the Roman Empire, believed to be the origin for the maxim "All roads lead to Rome".